Re-glazing a vintage timber sliding sash

[Possom]

The coating is applied to one surface only..yes

I have only ever seen 6.4 laminate with the coating facing out but in theory
If you can find a laminate manufacturer who will put the two 'k ' surfaces facing then yes it is possible...BUT and this is a very big but , it will cost an absolute fortune , as it will become a specialised glass. You will never see you money back from it!

Thanks very much. If I'm talking to glaziers about this, at least I'll now have some idea what I'm talking about! Thanks again!

 

[Possom]

One thing which occurred to me is would it be possible to install one pane of toughened Pilkington K glass with a sheet of the stick-on laminate film applied to the K side? Therefore eliminating the issue of cleaning a K sided pane.

This laminated K-side then pointed *into* the house to prevent moisture gathering under the film if pointed out.

The application of the film would add minimal additional weight, so presumably wouldn't upset the sash weights.

Though I wonder if the K side *must* be faced outwards as is usually the case, or if it only preferable to do so?

Or is K glass only 'effective within a double glazed unit only' which one glazier has informed me.

 

[ronniecabers]

Potentially you could put film over the ' k' surface, but you would need to clean it thoroughly to get all the dust etc off, and I fear this would scratch the surface, and you would also be back to the problem of potential bubbles ( as with the safety film )

The 'k' side facing out is a mute one , as many will say it has to, but many door/window sealed units that have been manufactured with decorative glass and an obscure backpane , since 2002, will have the 'K' surface the other way to this.

Despite many peoples beliefs 'k' glass can be used single glazed...as I stated before , our secondary glazing supplier does just this...

 

[Possom]

Due to the scratching risk when cleaning the K glass, I'm thinking my options are use

a) ordinary heat-treated single-pane toughened glass with secondary glazing
b) use ordinary 6.4mm laminate glass with secondary glazing

The glass used in b) are two sheets of 3mm, so 6mm total thickness of glass. The original single pane in a 1930s house, I wonder would this be the imperial equivalent of 6mm, or would it be thinner?

Do your suppliers of secondary glazing who use Pilkington K glass in single form experience issues with customers scratching this glass when cleaning it?

 

[ronniecabers]

Laminate glass would usually be 6.4mm and normal window glass would be 4mm , so thinner, and poss 1930's might be 3mm glass...so out of your optons the Laminate would be the thickest ( and heaviest )

Personally I would ( if funds allow! ) , change the panes to 4mm tough clear glass and then fit secondary glazing ( balanced vertical sliders ideally to match existing frames ) , utilising 4mm tough Pilk K glass ( to aid in heat retention )

As goes for the scratching of the single 'k' panes , where my secondary glazing supplier is concerned, that I can't answer, however I have never asked if it is a problem....but also the single face of the 'k' glass would be within the space between the secondary glazing and existing window and should not pick up as much dirt as the other surfaces...

 

[Possom]

Personally I would ( if funds allow! ) , change the panes to 4mm tough clear glass and then fit secondary glazing ( balanced vertical sliders ideally to match existing frames ) , utilising 4mm tough Pilk K glass ( to aid in heat retention )

So, a single pane of 4mm tough clear in the window, with the 4mm Pilk K glass in the secondary glazing. Is this what you mean?

I had a look for the balanced secondary glazing vertical sliders there, and they look quite good.

One glazier I've been speaking with suggested using a 6.4mm laminate made with Pilkington Optilam
http://www.pilkington.com/en-gb/uk/.../safety-security/pilkington-optilam#brochures

Though he said most probably my windows do not have wooden slips, and he'd have to use putty and not window tape. Though my concern with this, as I mentioned, is the potential leaching between the panes.

 

[ronniecabers]

So, a single pane of 4mm tough clear in the window, with the 4mm Pilk K glass in the secondary glazing. Is this what you mean?

Yes

Optilam is just bog standard Laminate Glass, most of Pilks glasses start with the word Opti...

You would indeed run the risk of leeching as has been discussed , and also the weights will need to be looked into ( due to the increased glass width ) , or the sliding sash wouldn't work probably

 

[Possom]

So, a single pane of 4mm tough clear in the window, with the 4mm Pilk K glass in the secondary glazing. Is this what you mean?

Yes

Optilam is just bog standard Laminate Glass, most of Pilks glasses start with the word Opti...

You would indeed run the risk of leeching as has been discussed , and also the weights will need to be looked into ( due to the increased glass width ) , or the sliding sash wouldn't work probably

Cheers!

 

[Possom]

I mentioned earlier that the previous occupant had sealed up all the sash windows with a mastic sealer.

Today I removed the mastic sealer from one of the windows.

The joint between the horizontal top beam of the bottom pane and the horizontal bottom beam of the top pane, there was mastic here too which I removed.

It was quite blowy today outside, and when I removed the mastic I could really feel the gusts of cold air coming through the gap. The mastic had to be removed to allow the window to open.

I realise the secondary glazing would reduce this, but is there any product for this joint at the two panes to stop the gusts of air coming in between them?

 

[Possom]

bear in mind 6.4 laminate is two pieces of 3mm glass with a 0.4mm saftey interlayer.

The glazier I have been speaking with informs me that the 6.4 laminate glass effectively acts as 1 piece of glass in that two 3mm pieces are heat bonded with safety film in between.

He said he has been using laminate with putty for over 30 years and has had no issues to date.

I don't know if this is because the leeching issue is quite rare, if he's been very lucky, or if the leeching takes a number of years to occur and so maybe he doesn't learn of it from past customers.

 

[Possom]

I telephoned another glazier to ask about single pane glazing, and I happened to mention the issue of putty leeching with laminate.

He said discolouration around the edges of laminate glass was due to moisture getting in, not putty.

He said putty is waterproof and therefore better at stopping the moisture getting in than glass tape.

Not sure what to think about that...